View the article online for updates and enhancements. Related contentLightweight design of automobile frame based on magnesium alloy R Lyu, X Jiang, O Minoru et al. Abstract. Lattice material infilling is an important way to achieve lightweight. Focusing on the problems of non-uniform arrangement and the finite element analysis (FEA) of lattice material in the parts, a lightweight design method based on lattice material is proposed with the spacecraft servo frame as the design object. Modal analysis and topology optimization are carried out according to the boundary conditions. The optimized density results are used to guide the design of lattice material parameters and arrangement. The equivalent mechanical properties of lattice material are obtained through the standard specimens experiments. The equivalent material FEA model of the lightweight servo frame is established, and the performance of the lightweight structure is tested by FEA simulation and experiment. The results show that under the impact condition, the lightweight servo frame meets the performance requirements and the simulation method through the equivalent material model is validated.
Nonlinear periodic structures can present abundant nonlinear wave physics. The model consisting of periodic bistable oscillators (i.e., the bistable periodic structure) is essentially different from those nonlinear periodic systems consisting of monostable oscillators due to multiple equilibria in bistable periodic structure. Despite the extensive attention received, properties of harmonic and shock wave propagation in bistable periodic structure, especially the randomness and tunability behind regularity, have not been fully understood. This article reports the answers based on numerical method. We consider the varying trends of the band gap, vibration center, wave amplitude, and transmission and show their effects on energy transport. We find that the snap-through behavior always presents local intrinsic randomness with the regularity in whole, that is, it does not happen in sequence. For both harmonic and shock wave, most energy is localized inside the snap-through oscillators that changes the regularity for energy transport and is meaningful for shock wave protection. Bistable periodic structure can present very low-frequency and broadband wave attenuation by shifting the initial frequency of the band gap to nearly zero through tuning the wave amplitude to a critical value, which offers dynamic tunability. The damping and intensity of the shock pulse have significant effects on the shock wave propagation. This work provides guidance for the design and application of bistable periodic structure for elastic wave attenuation and shock wave protection.
Mechanical metamaterials have attracted extensive attention. This paper reports a metamaterial with tunable elastic wave bandgaps based on bistable buckling structure. First, we find that deformation of two symmetric buckling shells is intrinsically asymmetric, which blocks the realisation of robust tunability. Based on an analytical model, we clarify that the mechanisms for this intrinsic asymmetricity are the bifurcations on force–deformation curves. Then we propose a superposition method of buckling shells, which can realise the symmetric deformation for robust tunable stiffness. Using this variable-stiffness oscillator, we design a metamaterial sandwich beam, and numerically and experimentally demonstrate its tunable bandgap for vibration suppression. This paper presents the unusual deformation process of buckling elements widely used for constructing metamaterials, and provides a robust way to realise metamaterials with tunable vibration bandgaps.
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